利用gem安裝mysql時的錯誤：
[[email protected] ruby]# gem install mysql
Building native extensions. This could take a while...
ERROR: Error installing mysql:
ERROR: Failed to build gem native extension.
/usr/bin/ruby extconf.rb
mkmf.rb can't find header files for ruby at /usr/lib/ruby/ruby.h
Gem files will remain installed in /usr/lib/ruby/gems/1.8/gems/mysql-2.9.0 for inspection.
Results logged to /usr/lib/ruby/gems/1.8/gems/mysql-2.9.0/ext/mysql_api/gem_make.out
解決方法：
yum install ruby-devel